Polar catastrophe, electron leakage, and magnetic ordering at the LaMnO$_3$/SrMnO$_3$ interface

TL;DR

This paper models the electronic and magnetic properties of the LaMnO$_3$/SrMnO$_3$ interface, revealing electron leakage, magnetic ordering changes, and half-metallic conduction due to polar catastrophe compensation and strain effects.

Contribution

It introduces a comprehensive model capturing the interplay of electronic reconstruction, magnetic ordering, and strain effects at the LMO/SMO interface, extending understanding beyond previous studies.

Findings

Polar catastrophe is quenched by electron accumulation at the interface.

Electron leakage induces ferromagnetism near the interface.

A half-metallic conduction band forms at the interface.

Abstract

Electronic reconstruction at the polar interface LaMnO$_3$/SrMnO$_3$ (LMO/SMO) (100) resulting from the polar catastrophe is studied from a model Hamiltonian that includes the double and super exchange interactions, the Madelung potential, and the Jahn-Teller coupling terms relevant for the manganites. We show that the polar catastrophe, originating from the alternately charged LMO layers and neutral SMO layers, is quenched by the accumulation of an extra half electron per cell in the interface region as in the case of the LaAlO$_3$/SrTiO$_3$ interface. In addition, the Mn e$_g$ electrons leak out from the LMO side to the SMO side, the extent of the leakage being controlled by the interfacial potential barrier and the substrate induced epitaxial strain. The leaked electrons mediate a Zener double exchange, making the layers adjacent to the interface ferromagnetic, while the two bulk materials away from the interface retain their original type A or G antiferromagnetic structures. A half-metallic conduction band results at the interface, sandwiched by the two insulating bulks. We have also studied how the electron leakage and consequently the magnetic ordering are affected by the substrate induced epitaxial strain. Comparisons are made with the results of the density-functional calculations for the (LMO)$_6$/(SMO)$_4$ superlattice.